1. Field
One or more aspects of the present invention relate to a magnetic head tracking control method, a servo signal verification method, a magnetic tape drive, and a servo writer.
2. Description of Related Art
In accordance with the trend toward higher recording density in the realm of information storage technologies, the data tracks of a magnetic tape designed in recent years should have extremely narrow widths. To enable the magnetic head to precisely follow such a narrow data track, a servo signal indicating a reference position of the data track is written beforehand in the magnetic tape. In a magnetic tape drive which records or retrieves data in the magnetic tape, a track-following servo control is exercised in which the servo signal recorded in advance is read out to work out an amount of deviation in position between the data track in which data is just to be recorded or retrieved and the magnetic head so that the magnetic head is regulated based on the amount of shift in position to follow the data track.
Such a servo signal is formed by writing a servo pattern at predetermined intervals in the direction of transport of a magnetic tape. In a magnetic tape for use in perpendicular magnetic recording (i.e., the magnetic tape in which a magnetic material contained in the magnetic tape is magnetized in a thickness direction of the magnetic tape to thereby record information), for example, the servo pattern may include a first portion magnetized in one direction of two opposite thickness directions of the magnetic tape, and a second portion magnetized in a direction opposite to the one direction. See JP 2009-20943 A, for example.
In a servo writer for writing a servo signal, a servo signal is written by a fixed servo signal write head in a magnetic tape that is being transported. Therefore, in order to accurately write a servo signal in the magnetic tape, the magnetic tape is transported with extremely high accuracy in position so that the magnetic tape being transported does not wobble from side to side or subject to change in transport speed. However, in actuality, the servo signal written in the magnetic tape being transported is inevitably subject to undesirable variations (fluctuation) in a direction of transport of the magnetic tape due to fluctuation in current-carrying time of the pulsed signal (recording current for each pulse) outputted to the servo signal write head and variation in tension of the magnetic tape.
The present invention has been made in an attempt to eliminate the above disadvantages, and illustrative, non-limiting embodiments of the present invention may overcome the above disadvantages and other disadvantages not described above.